Experimental pyelonephritis in the cat 2. Ultrastructural observations

An ultrastructural study was made of the renal cortical lesions in cats with pyelonephritis produced by experimental Escherichia coli infection and temporary renal obstruction. The most striking changes were interstitial fibrosis, thickening and folding of the tubular basement membrane, and atrophy of renal tubular epithelium. Interstitial inflammatory cells were mainly lymphocytes and plasma cells. Release of renal tubular lipid into the interstitium occurred commonly but did not appear to provoke additional cellular response. Glomerular changes included segmental sclerosis, wrinkling and collapse of basement membrane, thickening and fragmentation of Bowman's capsule, and periglomerular fibrosis. The changes described are similar to those which occur in a variety of human and animal nephropathies and represent non-specific responses to injury.